The goals of this research program include evaluation of possible enzymatic sources of singlet molecular oxygen (1O2) and investigation of any pathological damage that this reactive species might induce. The role of 1O2 in the photooxidative damage of membranes is also under investigation. In connection with our work on 1O2-mediated photooxidative damage of membranes, we have developed a hydrophilic polymer-immobolized photosensitizer which is suitable for photooxidation in aqueous solution. This sensitizer will prove particularly useful for studies of photodynamic action and reactions of 1O2 with biologically important substrates. The sensitizer is conveniently removed from reaction solutions by simple filtration. Hydrophilic polymer beads were prepared by copolymerization of chloromethylstyrene and the monomethacrylate ester of ethylene glycol with the bis-methacrylate ester of ethylene glycol as crosslinking agent. Reaction of the polymer with Rose Bengal gave the hydrophilic sensitizer, HP -Rose Bengal. Several substrates have been photooxidized in aqueous solution with this sensitizer. The quantum yield for 1O2 production with HP -Rose Bengal was determined to be 0.48. The enzymatic co-oxidation of 14C-labeled 9,10-anthracenedipripanoic acid, a water-soluble acceptor which exhibits specific 1O2 reactivity to form an endoperoxide, is under investigation. A study of the co-oxidation of this substrate in the presence of prostaglendin synthetase and arachidonic acid has recently been initiated in collaboration with Professor Sawrence Marnett, Department of Chemistry, Wayne State University. Preliminary results have provided evidence for the production of 1O2 in this system. The mechanism of 1O2 formation will be investigated. Studies of the co-oxidation of this substrate in the xanthine oxidase-acetaldehyde and xanthine oxidase-xanthine systems have failed to provide any evidence for 1O2 production in these systems, contrary to other reports. Enzymatic oxidation of this substrate leads rather to hydroperoxide products.